GABA regulates neural excitability and is known to be involved in a number of brain disorders including epilepsy. Therapeutic agents that modulate GABA receptors are currently used for sleep disorders, depression, mood disorders, and control of seizures, yet their mechanisms of action on the receptor are not well understood. As a basis for understanding these diseases and developing therapies, it is necessary to first elucidate the mechanism of GABA's interaction with its receptor. In order to do this, the GABA rho receptor, which forms a functional homomer, will be exogenously expressed in HEK cells and examined with electrophysiological methods. Chimera that switch portions of rho1 and rho2, as well as point mutations, will be constructed in order to determine the domains that are involved in receptor activation. Currents elicited by GABA will be measured and dose-response relationships of both wild-type and mutants will be determined. Regions that play a role in channel activation will be isolated by construction of progressively smaller chimera and point mutations. The single channel kinetics of wild type and select mutants will be studied to gain insight into the activation mechanism as well as the mechanism by which the mutations impair activation. The results from this project will lead to a better understanding of the structural domains and activation mechanism of the GABA receptor.